The present invention relates to a substrate provided with antireflection films and its production method. Particularly, it relates to a substrate provided with antireflection films which prevents the reflection color tone from becoming bluish even when the angle of incidence is small, which is thereby used suitably for a window of a transport such as a windshield of an automobile, and its production method.
Conventionally, since the reflectance of visible light (hereinafter sometimes referred to simply as reflectance) from the film face side (interior side) of a windshield of an automobile is high, the color tone of e.g. the interior has been limited to one based on dark tone color (such as black), in order to suppress reflection of the dashboard and its surrounding, and to increase visibility of the driver. That has significantly restricted the color of the car interior and significantly limited the design of an automobile.
It has also been desired to suppress reflection on a rear glass of an automobile although there is no problem in visibility of the driver.
In recent years, the setting angle of a windshield and a rear glass tends to be acute from the viewpoint of the appearance design, and accordingly the problem of the reflection on the interior face tends to be more significant.
Accordingly, it has been required to reduce the reflectance on the interior face of e.g. a windshield and to increase the allowable range of the interior design.
As a method to achieve such requirements, it has been known to form an antireflection film on the surface of e.g. a windshield. For example, the following methods have been proposed such as 1) a method of forming a transparent multi-layer antireflection film (JP-A-4-357134, JP-A-4-357135, JP-A-6-305775, JP-A-8-152501), and 2) a method of forming a transparent single-layer antireflection film.
On the other hand, a windshield or a rear glass for an automobile is required to shield the direct solar radiation light as much as possible from the viewpoint of the temperature in the car, and a green type heat absorbing glass is mainly used at present. Accordingly, it is desired that a windshield also is achromatic or green from the viewpoint of the appearance design of an automobile.
However, of the transparent film obtained by the above method 1) or 2), the reflection color tone tends to be bluish in a case where the angle of incidence of visible light is small, such as in a case of from 0xc2x0 to 30xc2x0 for example, and the above requirements can not be met with such a film.
Further, the method 1) is to form a known multi-layer antireflection film by wet method. In a case of forming three layers, the total film thickness is so thick as at least about 250 nm, and the cost required for the production is high.
In the method 2), in the case of the vacuum deposition, MgF2 may be coated. However, it is necessary to form a film on a hot substrate in order to make MgF2 have an adequate strength, and stability of the film thickness distribution which is characteristic of the deposition is inadequate, such being problematic in productivity.
On the other hand, a new type multi-layer antireflection film comprising a light absorbing film as a constituent has been proposed (JP-A-64-70701, U.S. Pat. No. 5,091,244). However, if this multi-layer antireflection film is directly applied to a windshield for an automobile, no adequate antireflection performance will be obtained in a case where the angle of incidence is great, or the reflection color tone tends to be yellowish or reddish.
Further, an antireflection film comprising the above light absorbing film absorbs light, whereby the transmittance tends to be low. A green type heat absorbing glass which is generally used for a glass for an automobile at present tends to slightly decrease the transmittance at the visible light region. Accordingly, if a light absorbing film and a heat absorbing glass are combined, the transmittance will be considerably low, and the combination may be restricted according to regulatory regarding the transmittance of a windshield for an automobile in each country.
Production of a windshield for an automobile most advantageously comprises coating on a flat glass substrate, followed by cutting, bending and lamination. However, no conventional antireflection film has a high heat temperature processing resistance to a high temperature of from 560 to 700xc2x0 C. during a bending step in production of a windshield for an automobile. For example, when tin oxide is used for an antireflection film as a material having a moderate refractive index, refractive index and other optical performances change due to crystallinity at a high temperature, and cracks or peeling may result on a film due to change in volume. Particularly, among glasses having a transparent multi-layer antireflection film obtained as mentioned above 1), a glass having at least three antireflection film layers has a total film thickness of at least about 250 nm and is so thick, and accordingly the film may have cracks during high-temperature bending step, and it is impossible to form such a film by the above step.
Further, a conventional antireflection film is by no means resistant to a heat treatment for tempering.
Under these circumstances, it is an object of the present invention to provide a substrate provided with antireflection films, which is excellent in antireflection performance to incident light at an oblique angle from the film face side, which has a high transmittance, and with which the reflection color tone does not tend to be bluish not only in a case where the angle of incidence of visible light from the non-film face side is great but also in a case where it is small.
Another object of the present invention is to provide a substrate provided with antireflection films, which is excellent in antireflection performance to incident light at an oblique angle from the film face side, which has a high transmittance, with which the reflection color tone does not tend to be bluish not only in a case where the angle of incidence of visible light from the non-film face side is great but also in a case where it is small, and which is excellent in heat resistance.
A further object of the present invention is to provide a method for easily producing a substrate provided with antireflection films, subjected to bending or tempering, which is excellent in antireflection performance to incident light at an oblique angle from the film face side, which has a high transmittance, and with which the reflection color tone does not tend to be bluish not only in a case where the angle of incidence of visible light from the non-film face side is great but also in a case where it is small.
A still further object of the present invention is to provide a glass for an automobile, which is excellent in antireflection performance to incident light at an oblique angle from the film face side, which has a high transmittance, and with which the reflection color tone does not tend to be bluish not only in a case where the angle of incidence of visible light from the non-film face side is great but also in a case where it is small.
The present invention provides (1) a substrate provided with antireflection films, which comprises a transparent substrate and at least two antireflection film layers deposited (coated) on one side of the transparent substrate,
wherein the reflectance on the film face of light incident at an angle of incidence of 5xc2x0 from the film face side is at most 6% at the entire wavelength region ranging from 400 to 480 nm.
The present invention further provides (2) a substrate provided with antireflection films, which comprises a transparent substrate and first and second antireflection film layers deposited (coated) in this order on one side of the transparent substrate,
wherein the first layer is a thin film having a refractive index of from 1.6 to 2.6 and a geometrical film thickness (hereinafter sometimes referred to simply as xe2x80x9cfilm thicknessxe2x80x9d) of from 1.1 to 1.9 times the film thickness as an antireflection condition as obtained from the following formula; and
the second layer is a thin film having a refractive index of from 1.4 to 1.56 and a film thickness of from 0.5 to 1.1 times the film thickness as an antireflection condition as obtained from the following formula:
d=xcex/[4n{1xe2x88x92(sin xcex8/n)2}1/2]
wherein d is a film thickness as an antireflection condition of each layer, n is a refractive index of each layer, xcex=550 nm and xcex8=60xc2x0.
The present invention further provides (3) the substrate provided with antireflection films according to the above item (1) or (2) which comprises a transparent substrate and first and second antireflection film layers deposited (coated) in this order on one side of the transparent substrate,
wherein the first layer is a thin film having a refractive index of from 1.6 to 2.6 and a film thickness of from 60 to 200 nm; and
the second layer is a thin film having a refractive index of from 1.4 to 1.56 and a film thickness of from 50 to 140 nm.
The present invention further provides (4) the substrate provided with antireflection films according to any one of the above items (1) to (3), which comprises a transparent substrate and first and second antireflection film layers deposited (coated) in this order on one side of the transparent substrate,
wherein the first layer is a thin film containing an oxide, an oxynitride or an oxycarbide of at least one element selected from the group consisting of titanium, silicon, zinc, aluminum, tin, zirconium, tantalum, tungsten, bismuth and niobium, or a nitride or a nitrogen carbide of at least one element selected from the group consisting of silicon, aluminum and boron.
The present invention further provides (5) the substrate provided with antireflection films according to any one of the above items (1) to (4), which comprises a transparent substrate and first and second antireflection film layers deposited (coated) in this order on one side of the transparent substrate,
wherein the second layer is a thin film containing an oxide of silicon.
The present invention further provides (6) a substrate provided with antireflection films, which comprises a transparent substrate and first and second antireflection film layers deposited (coated) in this order on one side of the transparent substrate,
wherein the first layer is a tin oxynitride film having a film thickness of from 104 to 124 nm; and
the second layer is a silicon oxide film having a film thickness of from 85 to 105 nm.
The present invention further provides (7) a substrate provided with antireflection films, which comprises a transparent substrate and first, second and third antireflection film layers deposited (coated) in this order on one side of the transparent substrate,
wherein the first and second layers are thin films having compositions which are different from each other, each having a refractive index of from 1.6 to 2.5, and at least one of the first and second layers having a film thickness of from 0.04 to 0.9 time the film thickness as an antireflection condition as obtained from the following formula; and
the third layer is a thin film having a refractive index of from 1.4 to 1.5 and a film thickness of from 0.4 to 1.1 times the film thickness as an antireflection condition as obtained from the following formula:
d=xcex/[4n{1xe2x88x92(sin xcex8/n)2}1/2]
wherein d is a film thickness as an antireflection condition of each layer, n is a refractive index of each layer, xcex=550 nm and xcex8=60xc2x0.
The present invention further provides (8) the substrate provided with antireflection films according to the above item (1) or (7), which comprises a transparent substrate and first, second and third antireflection film layers deposited (coated) in this order on one side of the transparent substrate,
wherein the first and second layers are thin films having compositions which are different from each other, each having a refractive index of from 1.6 to 2.5, and at least one of the first and second layers having a film thickness of from 2 to 95 nm; and
the third layer is a thin film having a refractive index of from 1.4 to 1.5 and a film thickness of from 44 to 138 nm.
The present invention further provides (9) the substrate provided with antireflection films according to the above item (1), (7) or (8), which comprises a transparent substrate and first, second and third antireflection film layers deposited (coated) in this order on one side of the transparent substrate,
wherein the first and second layers are thin films having compositions different from each other, each containing an oxide, an oxynitride or an oxycarbide of at least one element selected from the group consisting of titanium, silicon, zinc, aluminum, tin, zirconium, tantalum, tungsten, bismuth and niobium, or a nitride or a nitrogen carbide of at least one element selected from the group consisting of silicon, aluminum and boron.
The present invention further provides (10) the substrate provided with antireflection films according to the above item (1), (7), (8) or (9), which comprises a transparent substrate and first, second and third antireflection film layers deposited (coated) in this order on one side of the transparent substrate,
wherein the third layer is a thin film containing an oxide of silicon.
The present invention further provides (11) a substrate provided with antireflection films, which comprises a transparent substrate and first, second and third antireflection film layers deposited (coated) in this order on one side of the transparent substrate,
wherein the first layer is a tin oxynitride film having a film thickness of from 70 to 130 nm,
the second layer is a titanium oxide film having a film thickness of from 1 to 25 nm, and
the third layer is a silicon oxide film having a film thickness of from 80 to 130 nm.
The present invention further provides (12) a substrate provided with antireflection films, which comprises a transparent substrate and first, second and third antireflection film layers deposited (coated) in this order on one side of the transparent substrate,
wherein the first layer is a titanium oxide film having a film thickness of from 1 to 25 nm,
the second layer is a tin oxynitride film having a film thickness of from 70 to 130 nm, and
the third layer is a silicon oxide film having a film thickness of from 80 to 130 nm.
The present invention further provides (13) the substrate provided with antireflection films according to any one of the above items (1) and (7) to (12), which comprises a transparent substrate and first, second and third antireflection film layers deposited (coated) in this order on one side of the transparent substrate,
wherein the total thickness of the three antireflection film layers (sum of the film thicknesses of the first, second and third layers) is less than 250 nm.
The present invention further provides (14) the substrate provided with antireflection films according to any one of the above items (1) to (13), wherein each layer has an extinction coefficient of at most 0.05 at the visible light region.
The present invention further provides (15) a method for producing a substrate provided with antireflection films, which comprises subjecting the substrate provided with antireflection films as defined in any one of the above items (1) to (14) to a heat treatment to produce the substrate provided with antireflection films having bending or tempering applied thereto.
The present invention further provides (16) a method for producing a laminated glass, which comprises subjecting the transparent substrate provided with antireflection films as defined in any one of the above items (1) to (14) wherein the transparent substrate is glass, to bending into a three-dimensional curved shape by a heat treatment, and laminating the glass substrate provided with antireflection films subjected to bending and another glass substrate having approximately the same shape by means of an intermediate film.
The present invention further provides (17) a window glass for an automobile which uses the substrate provided with antireflection films as defined in any one of the above items (1) to (14).
Now, the present invention will be described in detail with reference to the preferred embodiments.